Field of the Invention
The invention relates to a drive train with a drive shaft, a drive machine, and with a differential gear unit with three drives and outputs, one output being connected to the drive shaft, one drive being connected to the drive machine, and a second drive being connected to an electrical differential drive.
The invention furthermore relates to a method for operating a drive train with one drive shaft, one drive machine, and with a differential gear unit with three drives and outputs, one output being connected to the drive shaft, one drive being connected to the drive machine, and a second drive being connected to an electrical differential drive.
Description of the Related Art
A frequently imposed demand on driven machines, such as conveyor equipment, for example pumps, compressors and fans, or such as mills, crushers, vehicles, or such as energy extraction facilities, etc., is a more efficient, variable-speed operation.
Furthermore, electrical machines are used as an example for drive machines used in this connection, but the principle applies to all types of drive machines, such as, for example, to internal combustion engines.
The most frequently used electrical drives are currently three-phase machines, such as, for example, asynchronous motors and synchronous motors. In order to be able to operate in a variable-speed manner, they are linked in combination with a frequency inverter to an electrical system. Variable-speed operation of the drive can be implemented with it, but the solution is expensive and associated with major adverse effects on efficiency.
A comparatively more economical alternative that is also better with respect to efficiency is the use of differential systems—for example according to AT 507 394 A. The heart of a differential system is a differential gear unit, which in one simple embodiment is a simple planetary gearing stage with three drives and outputs, one output being connected to the drive shaft of a driven machine, a first drive being connected to the drive machine, and a second drive being connected to a differential drive. Thus, the driven machine can be operated at a constant speed of the drive machine in a variable-speed manner by a variable-speed differential drive equalizing a resulting speed difference. This variable-speed differential drive is generally a three-phase machine that is small compared to the drive machine and that is linked to an electrical system by means of a correspondingly small frequency converter.
Frequency converters are, however, more fault-susceptible than electrical machines and have a much shorter service life.